467
FXUS01 KWBC 221943
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
343 PM EDT TUE AUG 22 2023
VALID 00Z WED AUG 23 2023 - 00Z FRI AUG 25 2023
...EXTREMELY DANGEROUS HEAT WILL PERSIST ACROSS A WIDESPREAD
REGION SPANNING FROM THE CENTRAL TO SOUTHEAST U.S. THIS WEEK...
...HEAVY RAIN AND GUSTY WINDS ASSOCIATED WITH TROPICAL STORM
HAROLD CONTINUE OVER SOUTH TEXAS TODAY...
...SCATTERED FLASH FLOODING CONCERNS EXIST ACROSS PARTS OF THE
GREAT BASIN AND SOUTHWEST...
A SEARING AUGUST HEAT WAVE IS SET TO CONTINUE THIS WEEK UNDERNEATH
A POTENT, POTENTIALLY RECORD BREAKING UPPER-LEVEL RIDGE ANCHORED
OVER THE MID-MISSISSIPPI VALLEY, WHICH WILL DRIVE OPPRESSIVE HEAT
FROM THE CENTRAL TO SOUTHEAST U.S. HIGH TEMPERATURES THROUGHOUT
THESE AREAS ARE FORECAST TO REACH INTO THE UPPER 90S AND LOW 100S
EACH DAY THROUGH THE END OF THE WORK WEEK. WHEN FACTORING IN
BRUTAL HUMIDITY LEVELS, MAXIMUM HEAT INDICES COULD APPROACH 120
DEGREES. WHILE IT IS NOT UNCOMMON FOR AUGUST TO FEATURE DANGEROUS
HEAT, THESE TEMPERATURES ARE EXTREMELY ANOMALOUS AND LIKELY TO
BREAK NUMEROUS DAILY AND POTENTIALLY MONTHLY RECORDS. IN FACT,
HIGHS ARE FORECAST TO REACH UP TO 20 DEGREES ABOVE AVERAGE
THROUGHOUT IOWA AND NEIGHBORING STATES OVER THE NEXT FEW DAYS.
VERY WARM OVERNIGHT TEMPERATURES ONLY DROPPING INTO THE UPPER 70S
AND LOW 80S WILL COMPOUND THE IMPACTS ASSOCIATED WITH THIS
POTENTIALLY DEADLY HEAT WAVE. HEAT ALERTS (EXCESSIVE HEAT
WARNINGS, WATCHES, AND ADVISORIES) HAVE BEEN ISSUED FROM
MINNEAPOLIS TO NEW ORLEANS, WHICH INCLUDES 17 STATES AND ROUGHLY
150 MILLION PEOPLE. IT IS IMPERATIVE TO TAKE THE HEAT SERIOUSLY
AND AVOID EXTENDED TIME OUTDOORS, AS TEMPERATURES AND HEAT INDICES
WILL REACH LEVELS THAT WOULD POSE A HEALTH RISK, AND BE
POTENTIALLY DEADLY TO ANYONE WITHOUT EFFECTIVE COOLING AND/OR
ADEQUATE HYDRATION. REMEMBER, HEAT IS THE
NUMBER-ONE-WEATHER-RELATED CAUSE OF DEATH IN THE UNITED STATES.
MEANWHILE, TROPICAL STORM HAROLD CONTINUES TO CHURN INLAND ACROSS
SOUTH TEXAS, WHERE CURRENT RADAR AND SURFACE OBSERVATIONS SHOW
BANDED HEAVY RAINFALL AND GUSTY WINDS WRAPPING AROUND THE
CIRCULATION. A FEW FLASH FLOOD WARNINGS ARE NOTED AROUND CORPUS
CHRISTI WHERE HIGH RAINFALL RATES ARE DRIVING FLASH FLOODS IN
URBANIZED AND COASTAL AREAS. A THREAT OF SCATTERED FLASH AND URBAN
FLOODING WILL CONTINUE THROUGH EARLY TOMORROW OVER SOUTH TEXAS AS
HAROLD TRACKS INTO NORTHERN MEXICO. TROPICAL STORM FORCE WINDS AND
PERHAPS A TORNADO OR TWO ARE ALSO EXPECTED TO THREATEN SOUTH TEXAS
FOR THE NEXT SEVERAL HOURS AS HAROLD MOVES INLAND. BY TOMORROW AND
THURSDAY, THE MID-LEVEL REMNANTS OF HAROLD AND ITS MOISTURE IS
FORECAST TO PUSH TOWARD THE SOUTHWEST AND SOUTHERN ROCKIES. THIS
MAY LEAD TO ADDITIONAL FLASH FLOODING CONCERNS, ESPECIALLY NEAR
THE MORE FLOOD-PRONE SLOT CANYONS IN UTAH ON THURSDAY WHERE A
SLIGHT RISK (LEVEL 2/4) IS IN EFFECT ON THURSDAY.
ACROSS THE NORTHERN GREAT BASIN AND INTERMOUNTAIN WEST TODAY,
SCATTERED FLASH FLOODING IS POSSIBLE AS ANOMALOUS MOISTURE CONTENT
AND UNIFORM SOUTHERLY FLOW SUPPORTS POTENTIALLY TRAINING
SHOWERS/THUNDERSTORMS. LOOKING FARTHER EAST, PRECIPIATION CHANCES
CONTINUE TO CIRCUMVENT THE STRONG UPPER HIGH OVER THE MIDWEST AND
PROGRESS FROM THE GREAT LAKES TODAY TO THE NORTHEAST/CENTRAL
APPALACHIANS BY WEDNESDAY AND THURSDAY. SOME OF THE STRONGEST
THUNDERSTORMS COULD YIELD ISOLATED INSTANCES OF FLASH FLOODING,
DAMAGING WIND GUSTS, AND SEVERE HAIL. THE WEST AND NORTHEAST WILL
ENJOY BELOW AVERAGE TEMPERATURES TO GO ALONG WITH THE RAIN CHANCES
AND CLOUDS, AS HIGHS FOR MOST LOCATIONS REMAIN IN THE 70S AND LOW
80S.
ASHERMAN/SNELL
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